With scale reduction of electronic apparatuses, a semiconductor device built therein requires miniaturization and high integration. In the second half of the year of 1990, the study of the practical use of a wafer level chip scale package (WLCSP) has been begun. The WLCSP is a chip size package (CSP) formed by the following method. According to the method, terminals and interconnects are formed before a chip is cut out of a wafer, and thereafter, the chip is cut out of the wafer.
On the other hand, the development of a stacked package (multichip package) has been made from the second half of the year of 1990. According to the stacking package, a plurality of semiconductor chips is three-dimensionally stacked; therefore, considerable miniaturization is realizable. A package using a through electrode has been proposed as this kind of stacking package.
In optical devices, the study of the WLCSP has begun around the year of 2000. A structure of glass+bonding layer+image sensor+through electrode, or a structure of an optical device including a through electrode and a light transmission support substrate is known. The technique using the electrode structure is called as through chip via (TCV) or through Si via (TSV).
According to the conventional TCV, in order to firmly connect a through electrode and an electrode pad connected thereto and to simplify the process, the shape for connecting the through electrode with the electrode pad has a simple serial structure.